Urethane rubber composition

ABSTRACT

A URETHANE RUBBER COMPOSITION FOR PEROXIDE VULCANIZATION IS SHOWN. IT INCLUDES A RUBBER COMPOSITION HAVING A URETHANE BOND AND A PHOSPHORIC ACID ESTER PLASTICIZER CONTAINING A DIVALENT, TRIVALENT OR TETRAVALENT METAL.

United States Patent U.S. Cl. 260-30.6 R 1 Claim ABSTRACT OF THEDISCLOSURE A urethane rubber composition for peroxide vu1canization isshown. It includes a rubber composition having a urethane bond and aphosphoric acid ester plasticizer containing a divalent, trivalent ortetravalent metal.

This is a continuation of application Ser. No. 59,673, filed July 30,1970 now abandoned.

This invention relates to a urethane rubber composition having improvedproperties, and more particularly to a urethane rubber composition incombination with a novel phosphoric acid ester plasticizer.

Casting type, thermoplastic and radical cross linking type urethanerubbers are well-known as unique rubbers which have excellent mechanicalproperties such as abrasion resistance and tensile strength as well asageing resistance, ozone resistance, oil resistance, solvent resistance,etc. Several kinds of radical cross linking type urethane rubbers areavailable on the market.

However, the available urethane rubbers have a very serious defect inthat their mechanical properties vary greatly at low temperature, ascompared with other synthetic rubbers such as polybutadiene, butylrubber, silicone rubber, etc. A rubber comprised of a blend consistingof, for example, 100 parts by weight of a radical cross linking typerubber, 30 parts by weight of carbon black, 3 parts by weight ofperoxide and 5 parts by weight of stabilizer and other blending agent,which is cross-linked at a temperature of 150 C. under a pressure of 35kg./cm. for 30 minutes, loses its elasticity when cooled down to atemperature of 20 C.

Accordingly, the primary object of this invention is to improve theplasticity, cracking resistance, cold resistance and tear resistance, ofvulcanized urethane rubber without impairing its tensile strength,elongation percentage, 100% modulus, permanent elongation, abrasionresistance, ozone resistance and oxidation resistance.

Another object of this invention is to provide a urethane rubbercomposition containing a plasticizer which achieves the above objectswithout hindering peroxide vulcanization.

These and other objects of this invention are achieved with a urethanerubber composition for peroxidevnlcanization which is comprised of arubber composition having a urethane bond and a phosphoric acid esterplasticizer containing a divalent, trivalent or tetravalent metal.

The urethane rubber of this invention is cross-linked with a peroxide,for example, diacyl peroxide, ester peroxide, acetal peroxide, dialkylperoxide, diarylalkyl peroxide, hydrogen peroxide or the like and acumene derivative is of particular utility for the cross-linking of theurethane rubber. In practice, dicumyl peroxide, tbutyl cumyl peroxide,thymyl cumyl peroxide, methyl cumyl peroxide and the like are employed.Dicumyl peroxide is especially effective for this purpose.

It has heretofore been known in the art to use compounds of thephosphorous ester system, phosphoric acid ester system, phosphorous acidester system and acid ester phosphate system as plasticizers forurethane rubber. The use of the phosphorous ester, phosphorous acid3,799,904 Patented Mar. 26, 1974 ester and acid ester phosphate systemsof compounds, interferes with radical cross linking by the peroxides,and vulcanized products of less than satisfactory properties areobtained. Accordingly, the compounds of the above three systems cannotbe used as plasticizers in urethane rubber compositions for peroxidevulcanization of this invention.

Of the remaining phosphoric acid ester system compounds, those havingprimary, secondary or tertiary amino radicals interfere with the radicalcross-linking, and accordingly, they too cannot be employed asplasticizers in urethane rubber compositions for peroxide vulcanizationof this invention.

The phosphoric acid ester system compounds which improve the propertiesof urethane rubber compositions for peroxide vulcanization andparticularly their cold resistance are disclosed in detail in copendingU.S. patent application Ser. No. 50,994 filed by the present applicationon June 29, 1970 and now abandoned.

The compounds which are used as plasticizers of urethane rubbercompositions for peroxide vulcanization according to this invention, arephosphoric esters containing divalent, trivalent or tetravalent metals.They are of the following chemical structure: phosphoric acid esters orphosphoric acid diesters, wherein the hydrogen atom of the hydroxylradical, in the free state, is substituted with a divalent, trivalent ortetravalent metal. When more than two phosphoric acid ester or diesterunits are combined, the product may be regarded as a salt of thephosphoric acid ester to which they are bonded through the metal atom.

The alcohol groups which constitute the esters of the phosphoric acidare alcohols of alkyl radicals, aryl radicals and alkoxy-alkyl radicals,which have two to eighteen carbon atoms. These radicals may besubstituted with halogens, hydroxyl radicals, cyano radicals or glycidylradicals. The metals in the plasticizer are divalent metals such aszinc, cadmium, lead, copper, nickel, cobalt etc. or trivalent metalssuch as aluminum or tetravalent metals such as titanium. Divalent metalsare preferred.

Zinc salts of phosphoric acid butyl ester are, for example, prepared byfirst reacting butanol with phosphorus pentoxide, thereby forming amixture of Zinc oxide is then reacted with the mixture of thesecompounds according to the following reactions:

In practice, Compounds I and II are mixed together, so that a morecomplicated compound may be considered as formed by the reaction of zincoxide with the monobutyl ester.

A urethane rubber, vulcanized by heating and pres- 3 surizing a urethanerubber composition of this invention, has superior qualities as comparedwith compositions not containing the recited plasticizers, especially intheir re- 4 PS=Permanent elongation (10 minutes after 100% elongated at25 C. or -20 C. for 10 minutes and returned to normal condition at thesame temperature) TABLE Rel. Ref. Rel. Ex. I Ex. II Ex. III Ex. IV Ex. VEx. I Ex. VI Ex. II Ex. VII Ex. III

Radical cross linking type methane rubber No. 1 100 100 Radical crosslinking type urethane rubber No. 2-- 100 100 100 100 100 100 Radicalcross linking type urethane rubber No. 100 100 Carbon l k 30 30 30 30 3030 30 30 30 30 st -1 m-id 0. 0. 5 0. 5 0. 5 0. 5 0. 5 0. 5 0. 5 0. 5 0.5 Antioxidant 2.0 2.0 2.0 2. 0 2.0 2.0 2.0 2.0 2.0 2.0 Blending:

Dicumyl peroxide 3. 0 3. 0 3. 0 3 0 3. 0 3. 3. 0 2-ethy1 hexyl zinephosp 10 Normal butyl calcium phosphate 2-ethyl hexyl cadmium phosphate10 2-ethyl hexyl aluminum phosphate 10 Normal butyl zinc phosph 10 10Properties:

Tn 213 195 221 229 215 260 235 285 180 203 En 380 410 405 355 360 320730 710 960 745 Tum 36 34 36 31 34 45 47 62 20 31 H C.) 70 67 69 68 6972 71 84 45 55 H (-20 C.) 74 69 72 73 73 79 75 93 49 70 PS (25 C.) 0.80.6 0.6 0.7 0.5 0. 6 2.0 2.0 3. 1 2. 5 PS (20 C.) 1.2 0.9 1.0 1.0 0.83.0 2.9 5.0 3.6 6. 0

sistance to cold. This is demonstrated in the following invention wereprepared as follows. 100 parts by weight of a radical cross linking typeurethane rubber, designated as No. 1, No. 2 or No. 3, parts by weight ofcarbon, 3 parts by weight of carbon, 3 parts by weight of diamylperoxide, 2 parts by weight of stabilizer and 10 to 20 parts by weightof metal salts of phosphoric acid esters, were milled to make urethanerubber compositions for peroxide vulcanization. Three referencecompositions without the salts were similarly prepared. The resultingurethane rubber compositions were vulcanized with a peroxide at atemperature of 150 C. under a pressure of kg./cm. for 30 minutes and theproperties of the vulcanized product were measured. The measured resultsare shown in the following table together with those of the referenceexamples. In the table, the following symbols have the indicatedmeaning.

T =JISK6301 (physical test for vulcanized rubber), tensile strength atbreak E =JISK6301 (physical test for vulcanized rubber), elongationcoefiicient T ==JISK6301 (physical test for vulcanized rubber),

modulus at 100% elongation H=JISK6301 (physical test for vulcanizedrubber), hardness As shown in the above table, the vulcanized productsof Examples I-VII have superior characteristics, especially coldresistance, as compared with the vulcanized products of the referenceexamples.

What is claimed is:

1. A urethane rubber composition for peroxide vulcanization comprisedof: a rubber composition containing a radical cross-linking typeurethane rubber; and, for each parts by weight of said urethane rubber,approximately 10 to 20 parts by weight of a phosphoric acid esterplasticizer selected from the group consisting of 2-ethyl hexyl zincphosphate, Z-ethyl hexyl cadmium phosphate, 2-ethyl hexyl aluminumphosphate, normal butyl calcium phosphate and normal butyl zincphosphate.

References Cited UNITED STATES PATENTS 3,647,745 3/ 1972 Jennings260-45.7 P

3,257,261 6/1966 Hochberg 260-4575 3,030,334 4/1962 Canaries 26045.75

3,470,222 9/1969 Jennings 260-4299 OTHER REFERENCES A. Damusis,Sealants, published 1967, Reinhold Pub., New York, pp. 144-5, 157-9,164-5.

MORRIS LIEBMAN, Primary Examiner P. R. MICHL, Assistant Examiner UNITEDSTATES PATENT OFFICE e CERTIFICATE OF CORREQTION Patent No. 3 799 904Dated March 26. 1974 .Inventorfis) It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

i In the Heading Insert:

--Priority: August 6, 1969 Japan 6l677/69-- Signed and sealed'this 24thday of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM F'0-1050 (10-69) USCOMM-DC eosve-pes U.S. GOVERNMENTPRINTING OFFICE: I969 o-ass-aaa,

